Sudden deaths!

[Alexa1s0nfire]

My girlfriend noticed one of our guppies was lethargic and looked pregnant (was just bloating as it was a male guppy) yesterday and saw it laying on the bottom of the tank. I noticed a piece of it's scales missing and it looked to have internal bleeding. (so sad) It did not last much longer. First thought was it got into a fight with either my gourami or another guppy. My gourami is the most timid mellow fish ever so I immediately dispelled that and then another one of the guppies all of a sudden was swimming funny and so I moved him to the QT and he didn't last long there either. Not sure what this is as my gourami and 6 julii's seem fine. Any Idea's?

checked params and ammonia was slightly up .25 - .50 did a 60% pwc immediately and got it below .25. (used ammo lock first) everything else seems in order.

 

[Alexa1s0nfire]

I also meant for a ? to be in the thread title not an !...not an exciting moment

 

[new to the scene]

if your fish was bloated maybe it has an internal parasite or bacteria or maybe due to fluctuations in water temp but not sure this is what i have heard around the scene i guess

 

[Alexa1s0nfire]

Temp stays right at 77-78 degrees and the fish were in there a solid week before this happened. I did add a dwarf gourami and 6 julii cory's a day prior to this. Wondering if that may have had an effect on them.